In recent years, in the field of automatic lathes (that is, lathes able to perform automatic machining) such as numerical control lathes (hereinafter called “NC lathes”), to enable machining of much more complicatedly shaped workpieces from a bar-shaped worked material (hereinafter called a “bar”), compound or combination machining where a large number of types of tools including rotary tools are provided on a tool rest to enable diverse automatic machining such as milling in addition to turning is being promoted. Further, to shorten the machining time, various multifunction type NC lathes carrying at least one spindle and at least one tool rest, which are operable under control in a plurality of paths or lines, close together on a single lathe bed, and capable of performing different types of machining (for example, outer circumferential turning and boring) simultaneously on the same bar or simultaneous machining on different bars have been proposed. Note that the term “line” means a combination of a group of control axes for control by a single machining program (including case of using only one control axis). When a plurality of types of combinations of such groups of control axes can be set on a single NC machine tool, the control system performed in this NC machine tool is generally called “multi-line control (or multi-path control)”.
As this type of multifunction type NC lathe, for example, there is known one provided with a main (or front) first spindle rotating while holding a bar supplied from outside the lathe, an auxiliary (or back) second spindle rotating while holding a partially machined bar received from the first spindle, and independently operating first and second tool rests equipped with pluralities of tools (for example, see Japanese Unexamined Patent Publication (Kokai) No. 10-315005 (JP10-315005A)). In this known NC lathe, the first spindle, second spindle, first tool rest, and second tool rest operate under control of two lines as explained later. Due to this, diverse automatic machining including simultaneous machining is performed.
Explaining this in more detail, the first spindle is configured to move linearly along a feed control axis (here, called the “Z1-axis”) parallel to its own axis of rotation. On the other hand, the first tool rest is configured to be located retracted to the side in the front of the first spindle in the axial direction and to move linearly along a feed control axis (here, called the “X1-axis”) perpendicular to the Z1-axis of the first spindle. The first tool rest is a so-called combtooth or gang tool rest holding a plurality of tools in a parallel arrangement and can mount a plurality of turning tools (or single point tools) in an arrangement enabling positioning perpendicular to the axis of rotation of the first spindle. Therefore, the first tool rest is capable of moving by interpolation the nose of a desired tool selected by indexing in accordance with an NC program by co-action between X1-axis motion of the first tool rest itself and Z1-axis motion of the first spindle controlled in the first line. Due to this, the bar held in the first spindle is machined to the desired shape.
The first tool rest further has a feed control axis (here, called the “Y1-axis”) perpendicular to both the Z1-axis and X1-axis. The Y1-axis motion of the first tool rest is motion to select the desired tool, and also functions, for example, as motion for cutting the outer circumference of the bar when selecting a rotary tool. Further, the first tool rest may have mounted to it additional tools in a combtooth manner at other positions for selection by X1-axis motion and motion by interpolation by Y1-axis motion.
The second tool rest is located away from the first tool rest in front of the first spindle in the axial direction. The second tool rest is a rocking type tool rest holding a plurality of tools in an arc arrangement centered on a rotation indexing control axis (here, called the “I-axis”) parallel to the Z1-axis of the first spindle and can mount at the front holding portion drills or other drilling tools in an arrangement enabling positioning coaxially with the axis of rotation of the first spindle. Therefore, the second tool rest is capable of moving relatively linearly the nose of a desired tool selected at the front holding portion by I-axis rotation in accordance with an NC program by Z1-axis motion of the first spindle controlled by the first line identical to the control line of the first tool rest for example. Due to this, the bar held in the first spindle is machined to be drilled in its end face.
The second tool rest further is capable of mounting similar drilling tools at a back holding portion at the opposite side to the front holding portion at the same positions as the plurality of tools for machining the bar held in the first spindle, coaxially but oriented in the opposite direction, to enable machining of a bar held in the second spindle. As opposed to this, the second spindle is configured having an axis of rotation parallel to the axis of rotation of the first spindle, located facing it coaxially in front of the first spindle in the axial direction, and moving linearly along a feed control axis (here, called the “Z2-axis”) parallel to the Z1-axis of the first spindle. Therefore, the second tool rest can move relatively linearly the nose of a desired tool mounted in the back holding portion in accordance with an NC program by Z2-axis motion of the second spindle controlled by a second line different from the first line. Due to this, end face drilling is performed on the bar held in the second spindle.
In this way, the above known NC lathe can control the motion of the spindles and tool rests along four feed control axes in two lines, in accordance with an NC program to simultaneously use as much as three tools selected on the two tool rests to automatically machine bars held at the two or front and back spindles.
In the above type of multifunction NC lathe, the respective operations of the spindles and the tool rests are normally controlled in accordance with respective machining programs input to a control unit (hereinafter called an “NC unit”), the programs being classified into lines to which they can belong. As an example, in the above-described NC lathe having two spindles and two tool rests, the data for machining a bar held in the first spindle by a tool mounted in the first tool rest is input as a machining program of a line-1 for controlling the X1-axis, Y1-axis and Z1-axis, the data for machining a bar held in the first spindle by a tool mounted in the front holding portion of the second tool rest is input as a machining program of the line-1 for controlling only the Z1-axis, and the data for machining a bar held in the second spindle by a tool mounted in the back holding portion of the second tool rest is input as a machining program of a line-2 for controlling only the Z2-axis. When manually inputting these data to the NC unit through a control panel (i.e., a manual data input), a display screen of the control panel generally displays the machining programs of the different lines as respective compact strings of blocks, in a plurality of program-describing areas provided serially or in parallel on the screen to be classified into the different lines.
In the past, manufacturers of multifunction type NC lathes have generally prepared software for NC units so that the above plurality of program-describing areas provided on the display screen of the control panel could only describe machining programs using control axes determined in advance corresponding respectively to the program-describing areas. Therefore, when for example a user input machining programs in the above two-line NC lathe, general practice had been for the machining programs by tools mounted in the first tool rest to be described in the program-describing area corresponding to the line-1, for the machining programs by tools mounted in the front holding portion of the second tool rest to be described in the same program-describing area corresponding to the line-1, and for the machining programs by tools mounted in the back holding portion of the second tool rest to be described in another program-describing area corresponding to the line-2. As a result, when inputting a machining program while checking the display screen of the control panel, the user had to first obtain an accurate grasp of the temporal relationship of the various types of control operations between different lines, that is, which is first or later or if they are simultaneous, then write them in the program-describing areas corresponding to the respective lines. As a result, an accurate understanding of the entire multifunction machining process and sufficient knowledge about the multi-line describing method has been required. Further, in this case, some NC units use specific codes for matching the timing of control among lines, so there was a tendency for the time for execution of a machining program (that is, the machining time) to become longer by the amount of the blocks describing these codes, the input work to become complicated, and input errors due to descriptive omissions to easily occur.
Further, in a conventional multifunction type NC lathe, when having a mechanical configuration enabling machining under control in several different lines for machining a bar held in one spindle, the lathe manufacturer generally prepared software for the NC unit so as to limit the line (or the combination of control axes) for controlling such a machining operation to a single line in advance. Therefore, the user was not given the freedom to select the line for control of the machining operation in that case. Further, in the case of control by superposition of axes in a conventional multifunction type NC lathe, the software of general NC units was prepared using specific codes for instructing the start and end of the superposition control, so there was a tendency for the time for execution of a machining program (that is, the machining time) to become longer by the amount of the blocks describing these codes, the input work to become complicated, and input errors due to descriptive omissions to easily occur.
Japanese Unexamined Patent Publication (Kokai) No. 2000-122709 (JP2000-122709A) discloses a method of describing multi-line machining programs in a multifunction type NC lathe. The method of describing disclosed in this publication enables simultaneous machining programs of two lines, classified and described into two program-describing areas in the past, to be described serially consecutively in a single program-describing area by use of specific codes (G185 and G186). This prior art, however, does not solve the various problems explained above occurring when a user prepares multi-line machining programs.